The present invention relates to self-extinguishing compositions based on thermoplastic polymer or on polymers showing elastomeric properties, particularly olefinic polymers or copolymers, containing salts of triazine compounds, optionally combined with reduced quantities of ammonium phosphates or of amine phosphates.
Different solutions are known in the art to reduce or remove the combustibility of polymers. Some of these solutions are based on the use of metal compounds, especially antimony, bismuth or arsenic, combined with organic compounds partially halogenated and thermically unstable, such as chlorinated parafinic waxes.
Other solutions are based on the use of substances able to produce intumescence. The formulations of the intumescent type are generally consisting of the polymer and of at least three main additives: one essentially phosphorated, the aim of which is to give, in combustion, an impermeable semisolid vitreous layer consisting essentially of polyphosphoric acid and to activate the process of intumescence formation; a second additive containing nitrogen which fulfills the function of foaming agent and a third additive containing carbon which acts as carbon donor for the char formation between the polymer and the flame.
Examples of intumescent formulations of this type are those described in U.S. Pat. No. 3,810,862 (Phillips Petroleum Co.) based on melamine, pentaerythritol and ammonium polyphosphate, U.S. Pat. No. 4,727,102 (Vamp s.r.l.) based on melamine cyanurate, a hydroxyalkyl derivative of the isocyanuric acid and ammonium polyphosphate and in the Published Patent Application WO 85/05626 (Plascoat U.K. Limited) based on different compounds of phosphorus and nitrogen, among which, in particular, a combination of melamine phosphate, pentaerythritol and ammonium polyphosphate.
In more recent formulations together the use of an organic or inorganic phosphorus compound an organic compound has been used containing nitrogen, generally an aminoplastic resin obtained by condensing urea, melamine or dicyandiamide with formaldehyde.
Examples of formulations comprising two additives are those described in U.S. Pat. No. 4,504,610 (Montedison S.p.A.) based on oligomeric derivatives of 1,3,5-triazine and ammonium polyphosphate and in European Patent 14,463 (Montedison S.p.A.) based on organic compounds selected from benzylguanamine and reaction products between aldehydes and different nitrogenous cyclic compounds, in particular benzylguanamine-formaldehyde copolymers, and on ammonium polyphosphate.
It is also possible to obtain self-extinguishing compositions using monocomponent additives, containing in the organic molecule both the nitrogen and phosphorus, as described in U.S. Pat. No. 4,201,705 (Borg-Warner Corp.).
These intumescent retarder system give the property of leading to the formation of a carbonaceous residue in the event of a fire or application of a flame to the polymer containing them. Retarder systems of this type have many advantages: absence of corrosion phenomena in apparatus wherein polymer are processed, lower smoke emission in comparison with systems containing metal compounds and halogenated hydrocarbons, and above all the possibility to confer satisfactory antiflame properties to polymers, using a lower quantity of total additive and therefore without excessive decay of the mechanical properties of the polymers themselves.